Embodiments of the present invention may relate to a test probe for a semiconductor package and, also to a test probe that may test electrical properties of a semiconductor package having ball-shaped input/output terminals.
Semiconductor devices are electronics that are typically packaged in semiconductor packages. The semiconductor package not only protects the semiconductor device from environmental conditions, but also provides interconnects for the semiconductor device to communicate with external hardware. Since a semiconductor device communicates through semiconductor package interconnects, the electrical properties of the semiconductor package greatly influence the operation of the semiconductor device. This influence is especially true for high-speed devices. Therefore, determination of semiconductor package electrical properties is relevant to managing semiconductor device performance. Ideally, a semiconductor package does not alter signal or power levels for a semiconductor device. In practice, the package may distort or lose signals or power for the device. This distortion and loss may be caused by various characteristics of the package, such as structure of transmitting lines, package element characteristics, etc. The factors that cause the distortion and loss are often referred to as parasitic parameters. Parasitic parameters may be represented by various quantitative models. Example models include an RLC circuit model, a frequency response model, and an impedance profile model.
Conventionally, probes with needle-shaped tips have been used to determine electrical properties and consequent parasitic parameters. A needle-shaped probe tip may touch terminals of a package, for example package pins, and form an electrical connection between the probe and package. Typical probes are GS and GSG probes, ground signal tips and ground signal ground tips, respectively, and the tips are generally arranged at fixed distances from each other. Package terminals spacing may vary considerably from package to package, and may not easily be measured by probes with fixed distances between measurement tips.
Currently, ball grid array (BGA) packages are widely used. A BGA package has an array of solder balls as input/output terminals, which is distributed over a package surface. The surface-distributed terminals reduce electrical signal propagation paths within the package and improve electrical and thermal properties. However, ball-shaped terminals may lose a good contact with the needle-shaped probe tips. Therefore, a conventional probe may often incorrectly measure the electrical properties of the package.